Women account for more than 11 million of incontinence cases. Moreover, a majority of women with incontinence suffer from stress urinary incontinence (SUI). Women with SUI involuntarily lose urine during normal daily activities and movements, such as laughing, coughing, sneezing and regular exercise.
SUI may be caused by a functional defect of the tissue or ligaments connecting the vaginal wall with the pelvic muscles and pubic bone. Common causes include repetitive straining of the pelvic muscles, childbirth, loss of pelvic muscle tone and estrogen loss. Such a defect results in an improperly functioning urethra. Unlike other types of incontinence, SUI is not a problem of the bladder.
Normally, the urethra, when properly supported by strong pelvic floor muscles and healthy connective tissue, maintains a tight seal to prevent involuntary loss of urine. When a woman suffers from the most common form of SUI, however, weakened muscle and pelvic tissues are unable to adequately support the urethra in its correct position. As a result, during normal movements when pressure is exerted on the bladder from the diaphragm, the urethra cannot retain its seal, permitting urine to escape. Because SUI is both embarrassing and unpredictable, many women with SUI avoid an active lifestyle, shying away from social situations.
SUI is categorized into three types. Type I and Type II are directed to urethral hypermobility. Type III is directed to intrinsic sphincter deficiency (ISD). Diagnosis of ISD requires urodynamic evaluation. Urodynamic evaluation involves complex and invasive equipment and often requires referral to a specialist trained in urodynamic evaluation.
Existing diagnostic systems all require a catheter be passed trans-urethraly to measure pressure, such as Leak Point Pressure (LPP) or Urethral Pressure Profile (UPP). An exemplary system is disclosed in publication (WO 0023127). Detection of LPP requires that a pressure sensor and catheter be passed trans-urethrally. The bladder is filled, and pressure is recorded. Fluid leakage from the urethral opening (meatus) corresponds to the maximum pressure the urethral sphincter can resist, or LPP. During the UPP measurement procedure a pressure sensor tipped catheter is placed trans-urethral into the bladder and then withdrawn at a constant velocity. The pressure profile along the urethra, from bladder neck to meatus is recorded.
Other parameters may also be measured, such as abdominal pressure and urinary flow. A cystometrogram (CMG) is a pressure study that simultaneously measures intra-abdominal, total bladder, and true detrusor pressures. Uroflometry measures urine flow rate visually, electronically, or via a disposable system. Video Urodynamic Systems also exist that simultaneously measure parameters, as described above, with radiographic visualization of the lower urinary-tract.
Existing urodynamic evaluation systems are complex, expensive, and require extensive training. Furthermore, existing urodynamic systems often require at least 30 minutes to complete a test. This exceeds the time available for most standard physician office visits and results in referral to a specialist. No urodynamic system exists that can quickly and inexpensively record useful urodynamic measures, without passing a catheter or instrument trans-urethraly.
Other than SUI, urge incontinence also accounts for a great number of cases of urinary incontinence. Urge incontinence is caused by overactive bladder muscles. Detrusor instability is one cause of urge incontinence. Detrusor instability involves spontaneous and unprovoked involuntary contractions of the detrusor muscle (the muscles that make up the bladder wall) during filling of the bladder that cannot be suppressed. Currently, diagnosis of detrusor instability similarly involves the use of invasive and uncomfortable transurethral catheters. The bladder is filled with fluid using such catheters, and the pressure is monitored to detects spikes in pressure, which indicate detrusor muscle contractions. Diagnosis using transurethral catheters is often complicated by the fact that the catheter often aggravates the delicate muscle structures of the urethral sphincter and bladder neck. Thus, the transurethral catheter actually aggravates and disrupts the very structures that the measurements seek to evaluate, potentially giving misleading results.
With regard to urge incontinence, there remains a need for an improved system and method for assessing detrusor instability.